(1) Field of the Invention
This invention relates to a separation roller set of an automatic document feeder (ADF), and more particularly relates to a separation roller set enabling feeding alignment.
(2) Description of the Prior Art
For early computer users, a scanner was a novel peripheral product and was mainly used by professional digital image operating users due to complex operating procedure. However, attending with the progressing of digital image technology, cheap and user's friendly scanners are available in the market and have become an indispensable part for personal users or small size offices.
Scanners at present may be briefly classified into feeder type and flatbed type. The flatbed type scanner has a design similar to a small-sized copier, which is characterized by placing papers, books, or documents on a glass plate to be scanned. Due to the advantages of small size and low cost, flatbed type scanner is more popular among self-employers. Nowadays, with the progress of scanning technologies, even the scanning of three-dimensional objects has become feasible for flatbed-type scanners.
In contrast with flatbed-type scanners, feeder-type scanners are mainly used in the environment of a large amount of sheet of papers to be scanned. A major advantage of feeder-type scanners is the so-called multi-page continuously scanning function, which leads to a relatively high scanning speed. However, due to the multi-page continuously scanning design, feeder-type scanners cannot be used to scan stapled documents, photographs, or three-dimensional objects.
FIG. 1 shows a sheet feeder 10 of a typical automatic document feeder (ADF) to facilitate multi-page scanning, which includes a pickup roller 12, a pickup arm 14, a separation roller 16, and a separation pad 18. The pickup arm 14 is pivotally connected to a shaft 16a of the separation roller 16. The pickup roller 12 is assembled to a movable end of the pickup arm 14. The separation pad 18 is a fixed element and can be divided into a feeding portion 18b and a separation portion 18a. There is a gap between the separation portion 18a and the separation roller 16 with the dimension ranged between the thickness of single sheet of paper and two sheet of papers.
As the sheet of paper S is fed, the movable end of the pickup arm 14 is declined along direction Y so as to have the pickup roller 12 attaching the sheet of paper S. The sheet of papers S are then driven by the pickup roller 12 along direction Z. The movement of the sheet of papers S is blocked by the separation pad 18 and the separation roller 16, and only the uppermost sheet of paper S can be carried through the gap between the separation portion 18a of the separation pad 18 and the separation roller 16 into the ADF.
However, the sheet feeder 10 cannot facilitate any aligning feature. In detail, the sheet of paper with some aligning error cannot be adjusted by the separation pad 18 to have the leading edge thereof parallel to the shaft of the separation roller 16.
Accordingly, it has become an important issue in the development of sheet feeder to prevent the problems of feeding misalignment and multiple feed.